Next story in Science

The idea of bringing extinct species back to life has
transitioned from science fiction to near reality in recent
years, with some scientists saying the passenger pigeon — a bird
that once clouded North American skies but went extinct due to
over-hunting in the early 1900s —could reenter the world within
the next several years.

But amidst the exciting prospects of seeing these
birds take to the skies again, or perhaps one day spotting a
woolly mammoth tromp through Siberia, some researchers have urged
those involved in so-called de-extinction to carefully consider
the ecological risks of reintroducing species to the wild —
before choosing to bring back any particular species.
Reintroduced species could pose risks by threatening other
animals (by preying on them or spreading parasites); endangering
humans with physical harm; or jeopardizing aspects of ecosystems
humans rely on. [ 6
Extinct Animals That Could Be Brought Back to Life ]

"This is very similar to any species you would reintroduce in the
world," Axel Moehrenschlager, a researcher at the Center for
Conservation Research at the Calgary Zoological Society in
Canada, told Live Science. "Whenever you put a species back into
a place where it has disappeared, there will be an array of
risks."

New guidelines

Moehrenschlager has worked with colleagues to develop a framework
of 10 questions that will help scientists systematically assess
the
ecological risks associated with introducing animals
back into the wild, based on questions used by the International
Union for the Conservation of Nature to assess the effects of
introducing existing species into new habitats.

The newly proposed questions address several topics: whether
enough is known about both
the cause of extinction and the ecological needs of
candidate animals to ensure healthy living moving forward; if
sufficient habitat exists for candidates in the modern world; if
humans will be harmed by reintroduction; if other species will be
harmed by reintroduction; and whether it will be possible to
remove the individuals in the event that they have a negative
impact.

The researchers tested the framework on three extinct species:
the
baiji dolphin, native to the Yangtze River in China; the
Xerces blue butterfly, native to coastal California; and the
thylacine, native to Tasmania, Australia. The baiji dolphin went
extinct in 2006, the Xerces blue butterfly in 1941 and the
thylacine in 1936.

The researchers chose these three species because they wanted to
assess a diverse sub-sample of animals that represented different
regions of the world and that went extinct at different points,
Moehrenschlager told Live Science.

Best candidates

From their assessment, the researchers found that not enough is
known about the baiji's decline to warrant de-extinction, but
that the Xerces blue butterfly and thylacine make good potential
candidates. Still, the scientists emphasize the results represent
just a preliminary screening, and that a more detailed review
would be needed before moving forward with these species.

As for the woolly
mammoth, Ross MacPhee, a zoologist at the American Museum of
Natural History who studies mammoths and was not involved in
creating the guidelines, says the mega-beasts would not likely
qualify under these guidelines, for a variety of reasons, the
most obvious of which is their large size. [ Woolly
Mammoth Comeback: 5 Ethical Challenges ]

"It's one thing to bring back a butterfly," MacPhee said.
"Mammoths are a whole different thing. Wherever it is put, it is
going to make a tremendous difference. I just don't see it being
particularly feasible."

Still, MacPhee does not think these drawbacks will stop
researchers from moving forward in trying to resurrect mammoths,
or from overlooking guidelines such as those proposed by
Moehrenschlager's team simply out of intrigue and excitement.

As of now, researchers are not legally required to consider these
suggestions, but Moehrenschlager's team hopes that researchers
will take it upon themselves to consider the guidelines as
research moves forward.

"We think the technology [for de-extinction] is evolving and that
it will likely happen, but what we want people to understand is
that this is a conservation translocation issue, and we should be
very systematic and thoughtful about what decision we make,"
Moehrenschlager said.

The guidelines are detailed in the March issue of the journal
Trends in Ecology and Evolution.

Editor's Note: This story has been
updated to clarifying that the guidelines are based on those
created by the International Union for the Conservation of Nature
(IUCN), not Science.